Assessment of Design Guidelines of Concrete Columns Reinforced with Glass Fiber-Reinforced Polymer Bars

Recent years have seen a great interest in testing concrete columns reinforced with glass fiber-reinforced-potymer bars (GFRP-RC). Yet, current codes and guidelines have not addressed the design of GFRP-RC columns. This paper aims at providing a set of recommendations and provisions based on analytical investigations, past knowledge about steel-reinforced concrete columns, and correlations with the experimental results from several studies of GFRP-RC columns. A database of 144 experiments was assembled; the results are reported and analyzed. The assembled database includes a selected number of parameters that can represent numerous practical cases. Based on this study, the calculation of the effective flexural stiffness (EIeff) was assessed with several equations and compared to experiments. As a result, a modified expression is recommended for EIeff at the factored load level. The design axial and flexural strengths were developed based on four approaches that were recently assessed with nominal and experimental results. It was found that the experimental-to-design strength ratio varied from 1.43 to 2.09. The minimum and maximum reinforcement limits were reviewed against the experimental results to ensure the integrity of the GFRP bars. In addition, the limits in the recent editions of ACI 318 and CSA A23.3 on steel transverse reinforcement (ties and spirals) were reviewed and mod fed to fulfill the performance requirements of GFRP tied and spirally reinforced columns.